Ambient high‐volume (hi‐vol) air samples were collected between 15 March and 30 May 2002, at Cheeka Peak Observatory (CPO), located on the tip of the Olympic Peninsula, Washington State. This sampling campaign was in conjunction with the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) campaign and the Photochemical Ozone Budget of the Eastern North Pacific Atmosphere 2 (PHOEBA2) experiment. The anthropogenic semivolatile organic compounds (SOCs) measured during this time period included polycyclic aromatic hydrocarbons (PAHs) and various U.S. current‐use and historical‐use pesticides. The total PAH concentration ranged from 0.480 to 4.49 ng/m3, which is comparable to other remote sites throughout the globe. Ten pesticides (hexachlorobenzene, dacthal, chlorothalonil, heptachlor, trans‐nonachlor, cis‐nonachlor, endosulfan I, triallate, trifluralin, and mirex) were also measured, and their concentrations (0.104–57.0 pg/m3) were comparable to other remote sites and less than agricultural areas. Gas‐phase/particle‐phase partitioning was explored, with significant correlation to temperature found with endosulfan I and retene and the possible relationship at CPO of low TSP concentration and the concentration of nonexchangeable compounds in the particle phase. Principal component analysis, as well as a t‐test, showed that there were elevated concentrations of anthropogenic SOCs measured during possible transpacific events on 15–16 March, 27–28 March, and 22–23 April 2002 that were identified using the GEOS‐CHEM model. The potential sources of these compounds at CPO were determined using diagnostic ratios of their concentrations, back trajectories calculated using Hybrid Single‐Particle Lagrangian Integrated Trajectory (HYSPLIT4), local meteorological conditions, and U.S. pesticide use data. Additional data are needed to confirm the sources of anthropogenic SOCs at CPO during regional and transpacific atmospheric transport events.
The trans-Pacific and regional North American atmospheric transport of polycyclic aromatic hydrocarbons (PAHs) and pesticides in biomass burning emissions was measured in air masses from April to September 2003 at two remote sites in western North America. Mary’s Peak Observatory (MPO) is located in Oregon’s Coast Range and Cheeka Peak Observatory (CPO) is located on the tip of the Olympic Peninsula in Washington State. During this time period, both remote sites were influenced by PAH and pesticide emissions from forest fires in Siberia and regional fires in Oregon and Washington State. Concurrent samples were taken at both sites on June 2 and August 4, 2003. On these dates, CPO had elevated gas phase PAH, alpha-hexachlorocyclohexane and retene concentrations (p<0.05) and MPO had elevated retene, particulate phase PAH and levoglucosan concentrations due to trans-Pacific transport of emissions from fires in Siberia. In addition, during the April to September 2003 sampling period, CPO and MPO were influenced by emissions from regional fires that resulted in elevated levoglucosan, dacthal, endosulfan and gas phase PAH concentrations. Burned and unburned forest soil samples collected from the regional forest fire area showed that 34 to 100% of the pesticide mass was lost from soil due to burning. These data suggest that the transPacific and regional atmospheric transport of biomass burning emissions results in elevated PAH and pesticide concentrations in western North America. The elevated pesticide concentrations are likely due to re-emission of historically deposited pesticides from the soil and vegetation during the fire event.
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